FOR YEAR 10B

NOVEMBER 2012

You just need to check your notes to answer this. Definition is in the beginning of your notes on this chapter, and we went through the main points for dialysis. Just memorise :)


MARK SCHEME


ANSWER:
a) Excretion is the removal of metabolic waste and toxic substances from the body of an organism  (3marks)

b)  The kidney machine filters waste substances from the blood. The blood is passed through a tubing that is partially permeable and bathed in a specially controlled dialysis fluid. Urea diffuses out of the blood, but glucose remains in the blood. Other large molecules also remain in the blood such as proteins. (7 marks)






This one is quite straightforward, your notes will have this :)

MARK SCHEME

a) The lock and key hypothesis explains the specificity of enzymes. The enzyme has an active site whose shape is complementary to the shape of the substrate. The substrate will fit into the active site and form an enzyme-substrate complex, and then products will be formed. (6 marks already!)

b) As temperature increases, the rate of reaction becomes faster. At optimum temperature, the rate of reaction is maximum. Beyond optimum temperature, the rate of reaction drops rapidly as the enzyme is denaturing. The reaction stops as the enzyme has lost its 3D shape and the substrate no longer fits. (7 marks!!! you only need 5 hehe)